Is It Ethical to Exclude Pregnant People From Research Simply to Avoid Additional Risk?

Is Exclusion Really the Safest Option During Pregnancy?

A clinical study involves a new intervention. Researchers know that pregnancy may introduce additional considerations, including possible effects on the fetus. The simplest protocol decision seems obvious: exclude anyone who is pregnant.

That certainly removes fetal exposure from the study.

But pregnant people still become ill. They still develop chronic conditions, infections, cancer, psychiatric disorders, cardiovascular disease, and conditions unique to pregnancy. They still need medications and other interventions. When research systematically excludes them, clinicians may eventually have to make treatment decisions without evidence generated in the population actually receiving treatment.

The ethical question is therefore more difficult than “How do we avoid research risk?” Researchers should also ask what risks are created by not doing the research.

Pregnancy Alone Is Not a Sufficient Reason for Automatic Exclusion

Protection From Research Can Become Exclusion From Evidence

Pregnancy changes risk assessment, not a person's capacity for autonomous choice

Pregnancy can change physiology, drug metabolism, pharmacokinetics, and the possible consequences of an intervention. Research may therefore need to consider both the pregnant participant and potential fetal effects.

Those considerations are ethically important. They do not mean that pregnancy itself makes a person incapable of understanding research or deciding whether to participate.

In the United States, the revised Common Rule no longer lists pregnant people among the populations described as vulnerable to coercion or undue influence. Separate federal protections continue to apply to research involving pregnant women, human fetuses, and neonates under 45 CFR Part 46 Subpart B.

The American College of Obstetricians and Gynecologists similarly argues that pregnant people should not be treated as though pregnancy undermines autonomous decision-making and recommends increasing their appropriate inclusion in research.

Trying to eliminate all fetal risk can create different risks outside research

A zero-risk standard sounds protective but is not realistic.

Pregnant people routinely require treatment. If they have been excluded from the research used to establish dosing, safety, effectiveness, and adverse-effect profiles, clinicians may have to extrapolate from evidence generated in nonpregnant populations.

Pregnancy itself can alter how medicines are absorbed, distributed, metabolized, and eliminated. Evidence obtained in nonpregnant adults therefore does not automatically answer every clinically important question during pregnancy.

ACOG argues that overemphasis on eliminating potential fetal risk can itself create harms because pregnant and lactating people may subsequently receive interventions without adequate evidence about their use in those populations.

There is an important difference between research risk and treatment uncertainty

Research ethics appropriately requires prospective assessment of risks before participants are exposed to an experimental intervention. Researchers should not use future knowledge as an excuse for exposing pregnant participants or fetuses to unreasonable risk.

But the comparison should not always be “research risk versus no risk.” For someone who has a serious illness during pregnancy, the real alternatives may include an inadequately studied treatment, an untreated condition, a treatment known to be less effective, or participation in carefully monitored research.

The ethically relevant baseline therefore depends on the participant's actual circumstances.

Some research questions cannot be answered without pregnant participants

Conditions unique to pregnancy provide the clearest example. Researchers cannot adequately study interventions for preeclampsia, pregnancy-specific pharmacology, labor, or other pregnancy-related conditions solely in nonpregnant participants.

ACOG notes that research conducted during pregnancy is the only opportunity to study interventions directed at conditions unique to pregnancy and describes greater inclusion of pregnant and lactating people as an ethical imperative for improving maternal and fetal health.

The scientific justification for inclusion can therefore be particularly strong when pregnancy is not an incidental participant characteristic but part of the phenomenon under investigation.

Even research on conditions not unique to pregnancy may need pregnancy-specific evidence

The argument for inclusion is not limited to obstetric research.

Pregnant people experience many of the same diseases as other adults. Yet physiological changes during pregnancy can affect treatment response, dosage, safety, and risk-benefit calculations.

The FDA notes that pregnant women have historically been excluded from drug-development trials while recognizing that inclusion can be scientifically and ethically appropriate in certain situations. In 2025, FDA published draft E21 guidance intended to facilitate appropriate inclusion or retention of pregnant and breastfeeding women in clinical trials so that evidence-based decisions can be made about medicinal products used by these populations. The guidance remains draft and nonbinding as of 2026.

Protection by exclusion can become a justice problem

Justice concerns both who bears research burdens and who has access to the opportunities and knowledge created by research.

If a population routinely uses healthcare interventions but is systematically absent from the research evaluating them, that population may bear the downstream consequences of uncertainty without having been allowed appropriate participation in producing the evidence.

ACOG explicitly grounds increased inclusion in justice and argues that fair distribution of research burdens and benefits supports equitable inclusion.

This illustrates why justice in participant selection concerns exclusion as well as inclusion.

Pregnant people should not be included regardless of risk either

Correcting historical exclusion does not mean swinging to the opposite extreme.

There may be strong reasons not to expose pregnant participants to a particular intervention. Preclinical evidence may suggest reproductive toxicity. Earlier human data may indicate fetal harm. The study may offer no prospect of direct benefit while exposing the fetus to more than ethically acceptable risk. Adequate preliminary safety information may not yet exist.

The relevant question is therefore not “Should pregnant people always be included?” It is whether exclusion has a scientifically and ethically defensible basis in this particular study.

Study design can reduce risk without resorting immediately to exclusion

Researchers have more than two options: include pregnant people under exactly the same conditions as everyone else, or exclude them completely.

Depending on the research, investigators may modify dosing, introduce additional monitoring, establish stopping criteria, stage enrollment until more safety information is available, collect pregnancy-specific pharmacokinetic data, use specialized consent information, or otherwise adapt the design.

ACOG emphasizes that appropriate study design can maximize the benefits of enrolling pregnant and lactating people while minimizing risks to pregnant participants, fetuses, and neonates.

The broader ethical task is therefore to determine whether risk can be responsibly managed before deciding that exclusion is necessary.

Exclusion criteria should explain why pregnancy matters to this study

A protocol stating “pregnant women excluded” has described a rule, not necessarily justified it.

The researcher should be able to explain the mechanism of concern. Is there evidence of reproductive toxicity? Is fetal exposure plausible? Is an imaging procedure involved? Would pregnancy substantially alter interpretation of the outcome? Is the investigational intervention contraindicated? Does the study involve a procedure carrying unacceptable pregnancy-specific risk?

That reasoning distinguishes a genuine ethically justified exclusion criterion from one retained merely because it is familiar.

When “Exclude Pregnancy” Is Easier Than Evaluating the Actual Risk

Common Misunderstandings About Pregnancy and Research Participation

Justify the Risk, Not the Habit

If your eligibility criteria exclude pregnancy, ask why before copying that criterion into another protocol.

The question is ultimately one of proportionate protection. Researchers should protect pregnant participants and fetuses from unreasonable research risks without protecting them out of the evidence base altogether.

This is a particularly clear example of why systematically excluding people most affected by a research question can itself become an ethical problem.

Before Excluding Pregnant Participants

Questions About Including Pregnant People in Research

Protecting Pregnant People Should Not Mean Automatically Excluding Them From Evidence

How to Cite This Guide

This guide is intended to be read, shared, and used in research, teaching, and academic work. If you draw on its ideas, explanations, or other content, please acknowledge the source by citing the guide. Doing so gives appropriate credit and helps your readers locate the original resource.